Epoxide hardener in silver halide emulsion layer and formaldehyde and/or glyoxal hardener in adjacent protective layer

ABSTRACT

THE PROCESS IN THE PREPARATION OF PHOTOGRAPHIC MATERIALS OF ADDING EPOXY COMPOUNDS HAVING HARDENING PROPERTIES OT A SILVER HALIDE EMULSION CONTAINING GELATIN, COATING A BASE WITH THE MIXTURE AND THEN COATING WITH A PROTECTIVE GELATIN LAYER CONTAINING FORMALDEHYDE OR GLYOXAL AS A HARDNER.

United States Patent Office 3,676,144 Patented July 11, 1972 US. Cl. 96-111 1 Claim ABSTRACT OF THE DISCLOSURE The process in the preparation of photographic materials of adding epoxy compounds having hardening properties to a silver halide emulsion containing gelatin, coating a base with the mixture and then coating with a protective gelatin layer containing formaldehyde or glyoxal as a hardener.

BACKGROUND OF THE INVENTION The present invention relates to a light-sensitive photographic material with reduced swelling.

In the preparation of photographic emulsions, it is customary to suspend the silver halide in polymeric binding agents. These binding agents may consist of gelatin, vinyl polymers, cellulose derivatives, and casein, among others, or mixtures thereof. All these materials have in common that they more or less swell in the presence of water, becoming permeable for dissolved particles and thus as a photographic layer make possible the developing process. The swelling of these layers is necessary on the one hand for the processability but is disadvantageous on the other hand due to the mechanical vulnerability of the expanded layers. For this reason, photographic materials are hardened in order to give them sufficient mechanical strength. High-speed processing of sheet film places particularly high demands on the mechanical stability of the expanded material. In addition, short drying times are required, which result only from a correspondingly decreased layer swelling. The hardening agents employed previously for this purpose were mainly Formalin, oxyaldehyde, dialdehyde, such as glyoxal and homologs, polymeric dialdehydes, chlorinated aldehyde acids, such as mucochloric acid and mucobromic acid, among others, polyfunctional acid chloride, activated silver halide compounds, chromium salts, divinyl sulfone, carbodiimide and diepoxide. All these hardening agents have in common that they react with functional groups of the gelatin side chains and effect thereby cross-linking which result in a raising of the fusion point, a decrease of the expansion and consequently a diminished vulnerability of the layer in the expanded state.

Of hardening agents described in the literature, relatively only a few have reached practical importance. This applies to the secondary requirements which are placed on good hardening agents aside from their crosslinking property, such as for example no damaging effect on the sensitometric properties of the emulsion, the highest possible hardening speed, non-toxicity, moderate volatility or none at all, strong reduction in the capacity to swell of the gelatins, no disadvantageous influence of the UV transmittancy of the hardened layer and no viscosity rise during storage time of the emulsion ready for pouring.

The object of the present invention was to synthesize a mechanically stable, as little as possible swelling layer without having to accept losses worth mentioning in sensitivity and gradation. In addition, the UV transmittal should not be encroached upon and one should be able to apply the layer with high speed, i.e. in very concentrated form.

SUMMARY OF THE INVENTION According to the invention, this is achieved by the combination of a hardening with formaldehyde and/or glyoxal over the protective layer and an epoxide hardening in the emulsion with compounds having at least two epoxide radicals which are obtained by the conversion of epichlorhydrin or epihydrinic alcohol with compounds containing amino, hydroxyl, carboxyl or sulfo groups or their functional derivatives, such as anhydrides, acid chlorides or betaines.

DETAILED DESCRIPTION OF THE INVENTION Examples of such compounds, as also disclosed in the German published application 1,095,113, among others, are as follows:

(1) Diglycide ether (2) Bis (2,3-epoxipropyl)-ethylamine (3) Ethylene glycol diglycide ether (4) Diethylene glycol diglycide ether (5) Phthalic acid diglycide ester (6) 2,4,6-triglycidylcyanourate The amounts to be used in these compounds are generally very low and may be easily ascertained by efforts in the customary manner. For the epoxides, they normally amount to 0.1-1.5 g. per g. gelatin of an emulsion ready for pouring. The corresponding amounts with respect to the protective layer are 0.6-6 g. formaldehyde or glyoxal to the epoxides may be varied as desired from 5:1 to 1:5.

It is essential in this connection that the addition of the epoxides to the concentrated emulsions, the viscosity per se during long standing at raised temperature does not rise at all or rises only moderately. The hardening sets in only during drying, the hardening speed being extraordinarily high and consequently the danger of subsequent hardening being low. With respect to most other hardening agents, an intensive cross-linking begins already in the liquid phase, something which results in a strong viscosity increase.

A further essential advantage of layers hardened in such a manner is their very good transmittal for UV light in the range of 300-400 me, which in the further processes of the photographic material, e.g. in copying processes, is of importance.

The particular advantage of the invention is that an optimum hardening effect is obtained when the hardening agents are distributed between two layers, and in particular the epoxide in the emulsion and Formalin and/ or glyoxal in the protective layer. Lesser expansion quotients are thus obtained with the same molar amounts.

The above-described emulsions, in addition to the hardening agents, may contain in a customary manner still further additives, such as optical and chemical sensitizers, coating auxiliary agents, and others. The novel protective layer, besides the hardening agents formaldehyde and glyoxal, may contain the customary binding agents, synthetic materials, delustering agents, coating auxiliary agents, filter dyes, and others.

EXAMPLE 1 A silver iodine bromide emulsion of medium sensitivity, ready for pouring, with 90 g. gelatin and ca. 60 g. AgNO per liter is divided into equal samples and to these are added the below-given amounts of epoxy compounds. These emulsions were subsequently poured on the base with a coating of 7.7 g. gelatin and 9.6 g. AgNO /m. Over that was drawn a protective gelatin layer which in addition to the necessary coating auxiliary agents contained 300 mg. formaldehyde as the hardening agent. After drying, the samples were stored at 22 C. and ca. 45% relative humidity and all samples were checked for their hardening condition after one week and after two months storage. For this purpose were considered the values of scraping resistance and swelling factor. They were determined in the following manner. In the measurement of the scraping resistance, the sample is swelled in water for 20 minutes at 20 C. and then scraped with a ball-bearing ball of 3 mm. diameter which cuts into the emulsion layer along its entire length down to the base, at which time the bearing pressure of the ball is read off. The swelling factor Q has been calculated from the swelling value Q according to Frieser among other (Photogr. Korrespondenz, vol. 2 (1963), p. 19) in accordance with the formula Wet strength after- Additive per 1. of Additive per 1. o! 1 week 2 mos. Q aitel protective coating emulsion (in pond) (in pond) 2 mos 0.3 g. CHzO- None 400 600 4. 18 Do 0.3 g. CHzO 800 1,000 3. 04 0.3 g. CHzO plus None 600 800 3.42

1.06 g. Epoxid Nr. 1. 0.3 g. CHgO. 1.35 mucoehiorie 800 800 3. 23

am Do 0.46 g. giyoxal 800 1,000 3.24 1.00 g. Epoxid Nr. 1- 800 1,000 3.0 Do 1.41 g. Epoxid Nr. 3.- 1, 000 1, 500 2. 30

To an emulsion according to Example 1 are added increasing amounts of the compound 4. Subsequently there occur a coating and an overlay with a protective layer, which per liter of solution contains 15 g. gelatin, wetting agent, SiO for roughening the surface, preserving agent as well as 200 mg. formaldehyde and 400 mg. glyoxal. The data obtained after the pouring and corresponding storage are given in the following table.

Wet strengths after- Swelling quotient 1 week 4 weeks 6 months after 6 Additive per 1. emulsion (in pond) (in pond) (in pond) months 1.5 g. Epoxid Nr. 4 600 1,200 1,500 2.97

2.8 g. Epoxid Nr. 4 800 1, 500 1,600 2. 64-.

5.6 g. Epoxid Nr. 4 1, 000 1,500 1,500 2.28

EXAMPLE 3 To an emulsion according to Example 1 are added the below-stated amounts of hardening agents, the mixture 4 is poured, and subsequently is coated with a protective layer according to Example 1. Particulars and results are given in the following table.

Molar Wet strength in wet storage after- Expansion It is recognized that with the use of equal molar amounts of hardening agents, the combination formaldehyde/epoxide yields the most advantageous values wit-h reference to the layer stability and layer swelling.

We claim:

1. A light-sensitive material comprising at least one light-sensitive silver halide emulsion layer having decreased expansion and improved UV transmittancy properties, which contains an epoxide hardener compound selected from those having the formula:

where R is =NR or 0, CR

R being a short chain alkyl group;

R being a short chain alkyl group with 2 to 5 C the light-sensitive material also having a protective gelatin layer contiguous with said silver halide emulsion layer and containing a hardener selected from the group consisting of formaldehyde and glyoxal in a molar ratio to the epoxide hardener of from 5:1 to 1:5.

References Cited UNITED STATES PATENTS 3,047,394 7/1962 Allen, et al. 96111 FOREIGN PATENTS 1,225,248 6/ 1960 France 96-l 11 1,095,113 12/1960 Germany 96ll1 NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R. 260-417; l06l25 

